Polyamide substrates, such as nylon carpeting, upholstery fabric and the like, are subject to staining by a variety of agents, e.g., foods and beverages. An especially troublesome staining agent is FD&C Red Dye No. 40, commonly found in soft drink preparations. Different types of treatments have been proposed to deal with staining problems. One approach is to apply a highly fluorinated polymer to the substrate. Another is to use a composition containing a sulfonated phenol-formaldehyde condensation product.
Examples of phenol-formaldehyde condensates are described in U.S. Pat. Nos. 4,501,591, 4,592,940, 4,680,212, 4,833,009. These materials are either condensation products of naphthalene monosulfonic acids with BHPS and formaldehyde or condensation products of phenolsulfonic acid with BHPS and formaldehyde. To impart stain resistance and solubility, the presence of sulfonic acid groups is necessary in these compounds, and the amount of sulfonation must be carefully controlled. These sulfonated condensates are themselves colored, often a deep brown, which can present a shade matching problem to the colorist.
Sulfonated phenol-formaldehyde condensation products are also subject to other undesirable color effects. Commonly they turn yellow on ageing after application to the fiber. Yellowing problems are described by W. H. Hemmpel in a Mar. 19, 1982 article in America's Textiles, entitled "Reversible Yellowing Not Finisher's Fault". Hemmpel attributes yellowing to exposure of a phenol-based finish to nitrogen oxides and/or ultraviolet radiation. To deal with the yellowing problem, the condensation products were modified by Liss et al in U.S. Pat. No. 4,963,409 and by Marshall in U.S. Pat. No. 4,833,009 to remove less active, highly sulfonated species. However, even after purification, yellowing remained a problem.
Moss III et al; in U.S. Pat. No. 5,015,259, disclose a stain-resist for polyamide fibers prepared by polymerizing an alpha-substituted acrylic acid or ester in the presence of a sulfonated aromatic formaldehyde condensation polymer. Fitzgerald et al., in U.S. Pat. No. 5,001,004, disclose the usefulness of aqueous solutions of hydrolyzed vinylaromatic/maleic anhydride copolymers in the treatment of textiles to render them resistant to staining. The preferred copolymer of Fitzgerald et al. is a hydrolyzed styrene/maleic anhydride copolymer. These compositions are effective against a variety of stains and do not tend to yellow significantly over time.
In U.S. patent application Ser. No. 07/626,885, filed Dec. 13, 1990, Pechhold discloses the utility of water-soluble or water-dispersible hydrolyzed maleic anhydride/alpha olefin polymers as stain-resist agents. And in U.S. patent application Ser. No. 07/634,794, filed Dec. 27, 1990, Pechhold discloses water-soluble or water-dispersible hydrolyzed maleic anhydride/vinyl ether or maleic anhydride/allyl ether polymers.
All of the polycarboxylate stain resists noted above function best when applied at low pH, and all suffer from a lack of fastness to an alkaline wash. Fitzgerald et al. (U.S. Pat. No. 4,883,839) describe the use of blends with sulfonated phenolic condensates to improve washfastness of the polycarboxylates.
The synthesis of monomeric carboxyalkylthiomethylated phenols has been described (Synthesis, April 1989, p 253 +ff), and carboxyalkylthiomethyl terminated polymers have been described (Demmer, U.S. Pat. No. 4,410,675), but none of these materials are stain resists.